La-doped Sr-hexaferrite(Sr_(1-x)La_xFe_(12)O_(19))(x=0.05,0.10,0.15,0.20) nanopowders with particle size ranging from 80 to 110 nm were successfully synthesized by sol-gel auto-combustion. The phase formation temperature increases, while the particle size decreases as the Ladoping content goes up. The partial substitution of Sr~(2+) by La~(3+) results in the suppression effects on the growth-up of the crystallites and the enhancement of the electron hopping between Fe~(3+) with different valences, which leads to the improvement in the dielectric loss and magnetic loss.Therefore, both the microwave absorbing abilities and absorbing frequency ranges are tuned by La-doping. The synthesized Sr-hexaferrite nanopowders with doping element content of 0.10 demonstrate the fine broad microwave absorbing properties. La-doped Sr-hexaferrite (Sr_ (1-x) La_xFe_ (12) O_ (19)) (x = 0.05,0.10,0.15,0.20) nanopowders with particle size ranging from 80 to 110 nm were successfully synthesized by sol-gel The partial formation of Sr ~ (2+) by La ~ (3+) results in the suppression effects on the growth-up of the crystallites and the enhancement of the electron hopping between Fe ~ (3+) with different valences, which leads to the improvement in the dielectric loss and magnetic loss. Beforefore, both the microwave absorbing abilities and absorbing frequency ranges are tuned by La-doping . The synthesized Sr-hexaferrite nanopowders with doping element content of 0.10 demonstrate the fine broad microwave absorbing properties.